Honest Auto Tech



Sunday, September 30, 2018

Cars A/C System, How does it works ?


Everyone enjoys long drives in the car in hot summers without being sweating and in chilled winters with hot suitable temperature, the car's  Air conditioning system is a necessity nowadays to keep you and your car's interior safe from outsides pollution, dirt, and dust.

Now you might be thinking
How does A/C of car works?  what are the Important parts? How to use it effectively?
Well for your all questions m having answers lets see it.

Cars Air-conditioning System

AC system
Image source: carhowto.com

It is designed for Human comfort, Packard invented automotive Air-conditioning system in 1939, and in 1940 it was the first car company to offer factory fitted AC, In India, back in 10 years it was less effective and efficient but now it is an integral system of car.
  1. let's see some aspects of how cars air conditioning is different from normal air conditioners.
  2. Vehicle design has to take into consideration the factors like coolant choice and temperature electric charging system, surge due to engagement/disengagement of compressor clutch.
  3. The AC components are subjected to vibrations and shocks due to movement of the vehicle.
  4. AC condenser has generally placed ahead of a radiator of the car. 
  5. Infiltration of air could be a major problem if the body design and door sealing are not carefully considered.
  6. Installation behind the dashboard and on the floor may be necessary. doors are generally not insulated and soundproofing lining of the roof may be adequate insulation.
  7. The air distribution in the small car is from outlets near the dashboard. The central one is for rear passengers and those at end of dashboards are for front seaters. In sedans, the trunk air conditioner may be a choice. In SUV's roof installation might give proper air distribution.

Our cars air conditioning system cools the cabin and takes out humidity from the air. The three basic components of refrigeration/ air conditioning system are Compressor, Evaporator, and Condenser, and a few other parts to keep the system running smoothly without any glitch.
Automobile air conditioning systems are mainly closed loops it has two sides one is the high-pressure side and one is the low-pressure side.
The high-pressure side is from to engine bay to the passenger compartment and low-pressure side is from the engine to radiator side.


 The reciprocating type compressor is a pump which is driven by a belt drive and should be capable of withstanding 7000rpm and also remain smooth and noiseless at low 600-700rpm. Magnetic clutch energized by engine power is the most common drive of the compressor.
When refrigerant comes in the compressor it is in a low-pressure gaseous form, it is compressed in the compressor, it pressurizes the gas and it is pushed into the condenser.


Due to condensers and radiators location, air flow to the radiator is restricted. The most commonly used condensers are Tube and fin and serpentine tube with brazed fins and its material is aluminum.
Radiator does the function of taking heat out from the system, as the refrigerant enters the condensers, when the gas is pressurized in compressor it creates some heat but air flowing around the twisting tubes of condenser cools the refrigerant gas again to liquid, now the liquid refrigerant is highly pressurized liquid which is ready to cool the car.


The high-pressure liquid refrigerant is sent through the receiver where the desiccants small granules are present which absorbs the water if water is kept in the system the ice crystals are formed and it may damage the whole air conditioning line. Sometimes receiver is also called as Dryer.

Expansion valve

Here system changes from high pressure to low pressure. The high-pressure gas coming from the receiver is passed through the expansion where it is allowed to expand, the expansion reduces pressure on the refrigerant and it can easily flow into the evaporator. The valve present here senses the pressure and regulates the flow of refrigerant. 


The type of evaporators is similar to the condenser. The evaporator must drain towards the outside, the blower capacity and evaporator size must take into consideration that due to suns direct heat through glass and cars body the cabin temperature could be high and this must be brought down quickly for the comfort of passengers. While all other parts of the system are located in the engine compartment, this is located in the cabin usually inside the dashboard.
Refrigerant enters the evaporator coil as a cold, low-pressure liquid, ideally at 32-degree Fahrenheit (0-degree Celsius),  which is why you don't want water molecules in the system. The refrigerant does not freeze at this temperature, but it does have a very low boiling point, The heat in the cabin of a car is enough to make the refrigerant R-134a in the evaporator to boil and a gas again, In its gaseous form a refrigerant can absorb a lot of heat.
The refrigerant gas moves out of the evaporator taking the heat with it. a fan blowing over the outside of the evaporator coil blows out cool air into the passenger compartment. The refrigerant in gas form then enters the compressor, where it pressurizes and the whole process starts again.

Some Precautions while using cars AC

  1. Use moderate temp level 24 degree Celsius it will give you better fuel economy. Fan speed does not make any effect on fuel economy.
  2. Never switch on AC at high speeds, which may result in seizing of the compressor.
  3. Never run AC without refrigerant otherwise compressor may seize.
  4. Do not use AC fresh air mode open always,
  5. Never operate AC with Heater on.
  6. Do not leave Ac joints open which may cause the moisture to enter the system.
  7. Do not charge the refrigerant in the AC system before flushing. 

Some Maintenance tips 

  1. Maintain proper belt tension. A loose belt will slip whereas tight belt will cause noise and premature compressor failure.
  2. Clean the condenser during normal servicing.
  3. Always maintain correct refrigerant level. Less refrigerant will give less cooling.
  4. Clean evaporator periodically.

If Any Queries related to topic feel free to ask in the comment section.
Keep reading keep sharing 


  1. That was actually important thing which most people ignore.. That was nice...

  2. It'll be very helpful to understand how it works..nd also what precautions we should take while using it..

  3. Hi,
    You have shared a informative information.Keep up with the good work. Check out the suv in india below 10lakhs

  4. mobil penumpang - The system conditions the air by cooling it and removing moisture to make you more comfortable while you drive. There are three types of air conditioning systems: orifice tube, expansion valve or a combination of the two which is found in rear air conditioning systems. The air conditioning system is made up of the following components: compressor, condenser, evaporator, orifice tube (or expansion valve), and an accumulator (or receiver-drier). Each of these components serves a different purpose


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